openstack/glance_store
Code Issues Proposed changes

S3: Fix multipart upload of 0 byte image

Browse Source 
When uploading a 0 byte image using multipart, we error out with
MalformedXML. A common case where this happens is when creating a
snapshot of a BFV server which in-turn creates a 0 byte image in
glance.
Multipart request is divided into 3 steps[1]:
1. CreateMultipartUpload
2. UploadPart
3. CompleteMultipartUpload

After completing the UploadPart step, we can see that the "Parts"
section of the request is empty eventually leading to MalformedXML.

'MultipartUpload': {'Parts': []}

To fix this, we need to handle the case when no Parts exist
and perform the following actions:
1. Abort the multipart upload
2. Initiate a single part upload with the 0 byte file

This doesn't affect the code path when image file is > 0 bytes
as we still execute the CompleteMultipartUpload step in that case.

Following are the success logs for the following operations:

1. Nova VM snapshot (Edge case handled in this patch):
INFO glance_store._drivers.s3 [None req-8f7e44f4-5f53-48f0-944d-5c6d5cdcb874 admin admin] Not doing multipart upload for zero-byte image key=bce3eb46-5542-42e6-a178-dbb44bc0587a, UploadId=MDA3MDNiNTUtZTIxZC00NDY2LTg2ZjQtZmFjYWMxNjkwMTMx
DEBUG glance_store._drivers.s3 [None req-8f7e44f4-5f53-48f0-944d-5c6d5cdcb874 admin admin] Creating zero-byte object directly using singlepart for key=bce3eb46-5542-42e6-a178-dbb44bc0587a {{(pid=2107463) _add_multipart /opt/stack/data/venv/lib/python3.10/site-packages/glance_store/_drivers/s3.py:856}}
INFO glance_store._drivers.s3 [None req-8f7e44f4-5f53-48f0-944d-5c6d5cdcb874 admin admin] Singlepart upload completed. Wrote 0 bytes to S3 key named bce3eb46-5542-42e6-a178-dbb44bc0587a with checksum d41d8cd98f00b204e9800998ecf8427e
INFO glance.location [None req-8f7e44f4-5f53-48f0-944d-5c6d5cdcb874 admin admin] Image format matched and virtual size computed: 0

2. Upload volume to image (Image file > 0 bytes):
INFO glance_store._drivers.s3 [None req-c4209dd7-3213-4590-a14e-d57c36803638 admin admin] Multipart complete key=14bf4232-9401-42bc-a7dd-aa811581ae55 UploadId=N2JhYmU3ZDAtNjI5My00MjZjLThhMGYtODlkODQzOTM0MTk5 Wrote 1073741824 bytes to S3 key named 14bf4232-9401-42bc-a7dd-aa811581ae55 with checksum cd573cfaace07e7949bc0c46028904ff

[1] https://docs.aws.amazon.com/AmazonS3/latest/userguide/mpuoverview.html#mpu-process

Closes-Bug: #2124829

Change-Id: I77d255d7c868779e9ea700ab83c7e77373fdffb5
Signed-off-by: Rajat Dhasmana <rajatdhasmana@gmail.com>
This commit is contained in:
Rajat Dhasmana
2025-09-17 14:22:38 +00:00
parent b320f11c8e
commit 342e95e1c1
3 changed files with 113 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files

51
glance_store/_drivers/s3.py
View File

@@ -835,28 +835,49 @@ class Store(glance_store.driver.Store):
total_size = sum(p.size for p in plist)
if success:
# Complete
pedict = {p.partnum: p.etag[p.partnum] for p in plist}
mpu_list = self._get_mpu_list(pedict)
s3_client.complete_multipart_upload(Bucket=bucket,
Key=key,
MultipartUpload=mpu_list,
UploadId=upload_id)
hash_hex = os_hash_value.hexdigest()
checksum_hex = checksum.hexdigest()
# Add store backend information to location metadata
metadata = {}
if self.backend_group:
metadata['store'] = self.backend_group
# If no parts were uploaded, this was a zero-byte image. This is
# the case when a BFV server creates a snapshot resulting in a 0
# byte image file. Since we cannot complete a multipart upload
# with zero parts, so we must abort it and create the empty
# object directly.
if not plist:
LOG.info("Not doing multipart upload for zero-byte image "
"key=%(key)s, UploadId=%(UploadId)s",
{'key': key, 'UploadId': upload_id})
s3_client.abort_multipart_upload(Bucket=bucket, Key=key,
UploadId=upload_id)
LOG.info("Multipart complete key=%(key)s "
"UploadId=%(UploadId)s "
"Wrote %(total_size)d bytes to S3 key "
"named %(key)s "
"with checksum %(checksum)s",
{'key': key, 'UploadId': upload_id,
'total_size': total_size, 'checksum': checksum_hex})
LOG.debug("Creating zero-byte object directly using "
"singlepart for key=%s", key)
s3_client.put_object(Body=b'', Bucket=bucket, Key=key)
LOG.info("Singlepart upload completed. "
"Wrote %(total_size)d bytes to S3 key "
"named %(key)s "
"with checksum %(checksum)s",
{'key': key, 'total_size': total_size,
'checksum': checksum_hex})
else:
# Complete the multipart upload
pedict = {p.partnum: p.etag[p.partnum] for p in plist}
mpu_list = self._get_mpu_list(pedict)
s3_client.complete_multipart_upload(Bucket=bucket,
Key=key,
MultipartUpload=mpu_list,
UploadId=upload_id)
LOG.info("Multipart complete key=%(key)s "
"UploadId=%(UploadId)s "
"Wrote %(total_size)d bytes to S3 key "
"named %(key)s "
"with checksum %(checksum)s",
{'key': key, 'UploadId': upload_id,
'total_size': total_size, 'checksum': checksum_hex})
return loc.get_uri(), total_size, checksum_hex, hash_hex, metadata
# Abort

72
glance_store/tests/unit/test_multistore_s3.py
View File

@@ -757,6 +757,78 @@ class TestMultiS3Store(base.MultiStoreBaseTest,
UploadId='UploadId'
)
@mock.patch.object(boto3.session.Session, "client")
def test_add_multipart_zero_byte_image(self, mock_client):
"""Bug #2124829: add a zero-byte image using multipart upload."""
expected_image_id = str(uuid.uuid4())
expected_s3_size = 0
expected_s3_contents = b""
expected_checksum = hashlib.md5(expected_s3_contents,
usedforsecurity=False).hexdigest()
expected_multihash = hashlib.sha256(expected_s3_contents).hexdigest()
expected_location = format_s3_location(
S3_CONF['s3_store_access_key'],
S3_CONF['s3_store_secret_key'],
S3_CONF['s3_store_host'],
S3_CONF['s3_store_bucket'],
expected_image_id)
image_s3 = io.BytesIO(expected_s3_contents)
self.config(group='s3_region1', s3_store_large_object_size=0)
self.store.configure()
fake_s3_client = botocore.session.get_session().create_client('s3')
with stub.Stubber(fake_s3_client) as stubber:
stubber.add_response(method='head_bucket',
service_response={},
expected_params={
'Bucket': S3_CONF['s3_store_bucket']
})
stubber.add_client_error(method='head_object',
service_error_code='404',
service_message='',
expected_params={
'Bucket': S3_CONF['s3_store_bucket'],
'Key': expected_image_id
})
stubber.add_response(method='create_multipart_upload',
service_response={
"Bucket": S3_CONF['s3_store_bucket'],
"Key": expected_image_id,
"UploadId": 'UploadId'
},
expected_params={
"Bucket": S3_CONF['s3_store_bucket'],
"Key": expected_image_id,
})
stubber.add_response(method='abort_multipart_upload',
service_response={},
expected_params={
'Bucket': S3_CONF['s3_store_bucket'],
'Key': expected_image_id,
'UploadId': 'UploadId'
})
stubber.add_response(method='put_object',
service_response={},
expected_params={
'Bucket': S3_CONF['s3_store_bucket'],
'Key': expected_image_id,
'Body': b''
})
mock_client.return_value = fake_s3_client
loc, size, checksum, multihash, metadata = \
self.store.add(expected_image_id, image_s3, expected_s3_size,
self.hash_algo)
stubber.assert_no_pending_responses()
self.assertEqual("s3_region1", metadata["store"])
self.assertEqual(expected_location, loc)
self.assertEqual(expected_s3_size, size)
self.assertEqual(expected_checksum, checksum)
self.assertEqual(expected_multihash, multihash)
@mock.patch.object(boto3.session.Session, "client")
def test_add_already_existing(self, mock_client):
"""Tests that adding an image with an existing identifier raises an

5
releasenotes/notes/s3-fix-issue-with-zero-byte-upload-6139250ef6e33c3c.yaml Normal file
View File

@@ -0,0 +1,5 @@
---
fixes:
- |
S3: Fixed issue when uploading a zero byte image using
multipart upload.